I recently read a long chapter on AP in a monograph by a Russian psychologist B.M.Teplov. Apparently his writings have not been translated and are relatively unknown in the West,for example he doesn't appear in our host's research bibliography on IP, nor in the bibliographyof Diane Deutsch's Psychology of musical ability scholarly volume.

The full title of the monograph is: B.M.Teplov, Psychology of musical abilities (1947). In Russian:Б.М.Теплов, Психология музыкальных способностей

Teplov was a seminal figure in Soviet psychology, and has a brief English Wikipedia entry at https://en.wikipedia.org/wiki/Boris_Teplov. I have the scanned book in Russian and can shareit with whoever's interested. More recent Russian articles about AP I briefly looked at (just two orthree of them, I'm far from being a thorough researcher of AP) invariably referred to Teplov.

Chapter 4 of the book consists of long and leisurely 30 pages of discussion of absolute pitch.Teplov reviews many experiments and conclusions of authors before him. Almost all of themare in Chris Aruffo's bibliography, though I think Carl Stumpf isn't there - Teplov references his studiesof AP in his Tonpsychologie (1883, 1890) in particular. He also mentions several Russianauthors and references both their and his own experiments with studying AP musicians andmeasuring the rate of AP among musicians.

I was particularly impressed by careful distinctions between different kinds of AP that Teplovattempts to draw, and the way he attempts to ground them on different (hypothesized) kindsof aural perception. I recently summarized these distinctions in English in a discussion elsewhere,and will quote this summary below in case it might be interesting. This is just the summary of hisconclusions, retold in my words - I didn't try to translate his careful supporting arguments.

====================I read a monograph by a Russian psychologist Teplov called “Psychology of musical ability” that has a chapter devoted to perfect pitch (no English translation alas). He goes into depth on what different kinds of perfect pitch he/other psychologists recognize and how they differ from each other. The most important difference he makes is between people who can instantaneously and w/o thinking tell you the note once they hear it, w/o invoking any memory of other notes, and people who can name notes, but compare it to their memory of other notes and apparently relying on relative pitch. This latter ability he calls pseudo-perfect pitch, and it always takes some thinking and at least 1-2 seconds of time. It isn’t as accurate as the instant-response kind.

The former ability, actual perfect pitch as he recognizes it, is pretty similar to how we can recognize the color red when we see it – we don’t need to compare it to anything in our memory. Now perfect pitch, acting without comparing to memory, he divides further into “passive perfect pitch” and “active perfect pitch”, where the passive one is when you can recognize but cannot sing a given tone without reference (either in reality or in your head from memory), and active is when you can both recognize and sing. You’re told “D” and you just sing it w/o thinking at all.

The passive perfect pitchers also seem to depend on timbre a lot – they often recognize piano, but not strings or (other people’s) voices, for example. So Teplov has a fascinating explanation for this (I don’t know how well it’s supported by other research). It has to do with how every sound actually generated in real life is never pure, but has its primary overtone and then its timbre, which is usually quite unique for that tone on that instrument (i.e. different notes on the piano have very different timbres, not just their common piano-timbre).

Suppose you’re a “normal” person, without perfect pitch. When you hear a sound, Teplov says, you hear its timbre “absolutely”, as something of its own that you can train to recognize (though it’s hard). But the actual pitch of the sound, the primary overtone, you can only hear “relatively” to some other sound.This means, staying with us non-perfect-pitchers for now, that you can actually learn to recognize a note if you practice really hard, but what you’ll learn to do, without maybe knowing it, is recognize the timbre. He describes several experiments where psychologists were able to get non-perfect-pitch people to decently recognize notes within two octaves, but they would describe their efforts at recognition as looking at how “light” or “heavy” or “bright” or “gloomy” the note is – metaphors associated with timbre.Unfortunately this ability, though it can be learned, never gets as good as perfect pitchers’ ability, and decays with time.

Now perfect pitchers, according to Teplov, have the neural networks trained (not his words) to recognize the actual pitch, the primary overtone, as a thing on its own and not relatively. But the difference between passive and active perfect pitch is that the passive ones still also use the timbre in identification – they don’t separate the pitch from the timbre in their perception, and so their neural network is kind of trained on both simultaneously. That’s why they get confused by other timbres and that’s why they can’t sing on request (because voice timbre is very different). Whereas active perfect pitch, the real “aliens” as far as I’m concerned separate the pitch from everything else and recognize that. And it seems to be completely inborn and can’t be learned (though you do need some early exposure to music to activate it).

The metaphor I made for myself trying to make sense of it is like this. It’s easy for us to recognize colors immediately. But suppose I gave you a list of 50 gradations of gray, from white to black, on the grayscale. It’s pretty easy to have “relative pitch” – to say which one is darker than the other, and even to “identify intervals” with some training. But even if you gave a separate name to each of the 50 grey shades, would you be able to recognize it? Having perfect pitch is like having each gray shade a separate thing in your perception, clearly identifiable, just as ‘red” and “green” are for us. Teplov goes into a lot of detail into how children with perfect pitch don’t need to “train” to improve it, seemingly they just need to know the names. They “see” the pitches as perfectly separate nameable entities from birth, they just need a guidance with naming. ”

To sum up, Teplov distinguishes these four distinct abilities, in order of decreasing awesomeness:

1. Active perfect pitch: able to instantly recognize note played on any instrument, and sing a note on request. Doesn't use relative pitch. Based on the ability to isolate the musical pitch from the timbre and perceive the pitch alone "absolutely".2. Passive perfect pitch: able to instantly recognize note played on some instruments, often not others and not voice. Can't sing a note on request. Doesn't use relative pitch. Based on "absolute" perception of the musical pitch, but heavilysupported at the same time by the recognition of the familiar timbres: pitch and timbre aren't separated in perception.3. Pseudoperfect pitch: able to recognize notes with significant delay, at least a few seconds and sometimes much more. Consciously utilizes relative pitch to compare against reference note, either held in pitch memory or produced by "inner singing".4. Trained "perfect pitch": people who practiced note recognition and achieved some success, invariably much more limited than real perfect pitch. Their recognition is based on timbre alone, and decays quickly after practice is stopped.====================